He should have the immortal promotion, he should be able to get XP, he should have 50 base strength, with ice strength thrown on top, he should have blitz as a starting promotion.
I know his blizzard spell can kill, but it doesn't compare to, say, the power of an army of self replenishing werewolves with Duin and some AOE mages following them. Even Drifa is more bad ass than Auric once she has all five combat promotions and some of the other stuff.
Really, if you invest 80,000 beakers or whatever (definitely a lot of beakers), get yourself in war with every race in the game and you get the 'The world considers you evil' unhappiness in your cities, then there should be a little more... oomph to him.
As the Illians, you cities should be a means to an end. Once you get the Auric, high priests of winter and Drifa you should be nigh unstoppable, rampaging through the world, and the only thing that can destroy you is the Godslayer.
On the flip side, there should be no feasible way to get out of war once the Draw is built (Seven Pines or becoming a vassal). It has to be like when Cortez burned his ships once arriving in South America, telling his men there was no way back until got what they came for (in this case, the Illians winning via conquest). And if the Godslayer is destroyed, then it is rebuilt again after a set number of turns in a distant city, and the civilisations can try again.